NOTE: As their name suggests hints are not exactly Resident Evil 6 cheats, and are usually just simple (but very useful) tips on how you can unlock secret level, features, find hidden areas and such. Hopefully these will make playing Resident Evil 6 even more entertaining.

Achievements: Onslaught Mode DLC
Kill or Be Killed (10): Win while in the dying state.
Killer Combo (30): Achieve a 30-combo chain.
Surrounded on All Sides (45): Send 2,000 enemies to your opponent's map.
Take the Stage (30): Defeat your opponent and achieve victory in 3 stages.
You Are S.O.L. (10): Defeat your opponent 10 times with enemies you sent.

Achievements: Predator Mode DLC
Easy Pickings (30): Eliminate all players as Ustanak in less than a minute.
Held Captive (10): Defeat Ustanak with only one Agent remaining.
Invincible (30): Defeat Ustanak without anyone on your team being captured.
Not without a Fight (45): Defeat Ustanak 20 times.
One Is Never Enough (10): As Ustanak, capture a total of 50 humans.

Achievements: Survivors Mode DLC
Kung Fu Fighting (30): Survive to the end only using physical attacks.
Last Man Standing--Again (45): Win five times in a row.
Staying Alive (10): Return to the game as a human character.
Take 'Em All Down (30): Defeat 100 agents.
Team Effort (10): Win without any members of your team being killed.

Mercenaries Characters
This is how to unlock the characters for the mercenaries game mode. Leon, Chris and Jake are unlocked by default.